Drug delivery device

ABSTRACT

A drug delivery device for selecting and dispensing a number of user variable doses of a medicament includes a dose limiter for preventing the setting of a dose, which exceeds the amount of liquid left in a cartridge of the drug delivery device. The device includes a cartridge containing liquid, a dosing element, which rotates during dose selecting, a last dose nut coupled to the dosing element during dose selecting such that rotation of the dosing element causes an axial movement of the last dose nut, and a stop element, which is provided on the dosing element and which blocks further movement of the last dose nut, if a dose is selected corresponding to the amount of liquid left in the cartridge. The device further includes a last dose sleeve rotationally coupled to the dosing element during dose selecting and rotationally decoupled from the dosing element during dose dispensing.

TECHNICAL FIELD

The present disclosure is generally directed to drug delivery devices for selecting and dispensing a number of user variable doses of a medicament.

BACKGROUND

Pen type drug delivery devices have application where regular injection by persons without formal medical training occurs. This may be increasingly common among patients having diabetes where self-treatment enables such patients to conduct effective management of their disease. In practice, such a drug delivery device allows a user to individually select and dispense a number of user variable doses of a medicament. Some aspects of the present invention are not directed to so called fixed dose devices which only allow dispensing of a predefined dose without the possibility to increase or decrease the set dose.

There are basically two types of drug delivery devices: resettable devices (i.e., reusable) and non-resettable (i.e., disposable). For example, disposable pen delivery devices are supplied as self-contained devices. Such self-contained devices do not have removable pre-filled cartridges. Rather, the pre-filled cartridges may not be removed and replaced from these devices without destroying the device itself. Consequently, such disposable devices need not have a resettable dose setting mechanism. Certain aspects of the present invention are applicable for both types of devices, i.e. for disposable devices as well as for reusable devices.

A further differentiation of drug delivery device types refers to the drive mechanism: There are devices which are manually driven, e.g. by a user applying a force to an injection button, devices which are driven by a spring or the like and devices which combine these two concepts, i.e. spring assisted devices which still require a user to exert an injection force. The spring-type devices involve springs which are preloaded and springs which are loaded by the user during dose selecting. Certain aspects of the present invention are applicable for all of these types of devices, i.e. for devices with or without a drive spring.

These types of pen delivery devices (so named because they often resemble an enlarged fountain pen) are generally comprised of three primary elements: a cartridge section that includes a cartridge often contained within a housing or holder; a needle assembly connected to one end of the cartridge section; and a dosing section connected to the other end of the cartridge section. A cartridge (often referred to as an ampoule) typically includes a reservoir that is filled with a medication (e.g., insulin), a movable rubber type bung or stopper located at one end of the cartridge reservoir, and a top having a pierceable rubber seal located at the other, often necked-down, end. A crimped annular metal band is typically used to hold the rubber seal in place. While the cartridge housing may be typically made of plastic, cartridge reservoirs have historically been made of glass.

The needle assembly is typically a replaceable double-ended needle assembly. Before an injection, a replaceable double-ended needle assembly is attached to one end of the cartridge assembly, a dose is set, and then the set dose is administered. Such removable needle assemblies may be threaded onto, or pushed (i.e., snapped) onto the pierceable seal end of the cartridge assembly.

The dosing section or dose setting mechanism is typically the portion of the pen device that is used to set (select) a dose. During an injection, a spindle or piston rod contained within the dose setting mechanism presses against the bung or stopper of the cartridge. This force causes the medication contained within the cartridge to be injected through an attached needle assembly. After an injection, as generally recommended by most drug delivery device and/or needle assembly manufacturers and suppliers, the needle assembly is removed and discarded.

The dosing section of drug delivery devices for selecting and dispensing a number of user variable doses of a medicament often comprises a display for indicating the selected dose to a user. This is especially important where a user may select a different dose each time depending on the state of health. There are mechanical displays, e.g. a drum with printed numbers on its outer surface, wherein the number corresponding to the actually selected dose is visible through a window or opening in the device. Although such mechanical displays are simple and reliable, they usually require a relatively large construction space which makes the devices bulky. In addition, the size of the numbers is in some cases too small for visually impaired users. Further, electronic displays are known, e.g. LCD displays, which have the benefit of a relatively large number size without requiring too much construction space. However, a downside of electronic displays is that they require an energy source and that such electronic components may be too expensive, especially in a disposable drug delivery device.

A disposable drug delivery device for selecting and dispensing a number of user variable doses of a medicament according to some aspects of the present invention typically comprises a dose limiter for preventing the setting of a dose, which exceeds the amount of liquid left in a cartridge of the drug delivery device. The device may comprise a dosing element, which rotates during dose selecting, a last dose nut (e.g. releasably) coupled to the dosing element during dose selecting such that rotation of the dosing element causes an axial movement of the last dose nut, and a stop element, which blocks further movement of the last dose nut, if a dose is selected corresponding to the amount of liquid left in the cartridge.

A disposable drug delivery device with a dose limiter is known e.g. from WO 2004/078241 A1. The dose limiter of this device includes a last dose nut which is in threaded engagement with a drive sleeve and splined to the housing. The drive sleeve is rotated during dose selecting and travels only axially during dose dispensing. Rotational hard stops of the last dose nut and the drive sleeve interact to prevent further rotation of the drive sleeve relative to the housing if a user sets a dose corresponding to the usable amount of liquid in the cartridge.

Further, WO 2001/019434 A1 describes an injection device with a dose limiter. The injection device is the type where a dose is set by rotating a dose setting member relative to a driver and away from a fixed stop in the injection device. The dose setting member interfaces the driver such that the dose setting member can be rotated in one direction without rotating the driver. The dose is injected by rotating back the dose setting member which during the backward rotation carries the driver with it. Rotating the driver causes the piston rod to move forward inside the cartridge and expel some of the liquid contained in the cartridge. The driver is provided with a track having a length which is related to the total amount of liquid in the cartridge and which track is engaged by a track follower coupled to the dose setting member to follow rotation of this dose setting member. Each time a dose is set and injected, the track follower moves further into the track. When the track follower reaches the end of the track the dose setting member cannot be rotated further, and a dose larger than the remaining liquid in the cartridge cannot be set.

In some cases it might be possible for the user to over-tighten this last dose protection mechanism resulting in device jamming.

SUMMARY

Certain aspects of the present invention provide drug delivery devices with improved and reliable dose limiters, i.e. last dose protection mechanisms.

This disclosure describes an example of a drug delivery device having a dose limiter for preventing the setting of a dose, which exceeds the amount of liquid left in a cartridge of the drug delivery device.

According to a first embodiment of the present invention, this object is solved by a drug delivery device comprising a cartridge containing liquid, preferably a medicament, a dosing element, which rotates during dose selecting, a last dose nut coupled to the dosing element during dose selecting such that rotation of the dosing element causes an axial movement of the last dose nut, a stop element, which is provided on the dosing element and which blocks further movement of the last dose nut, if a dose is selected corresponding to the amount of liquid left in the cartridge, and a last dose sleeve rotationally coupled to the dosing element during dose selecting and rotationally de-coupled from the dosing element during dose dispensing, wherein the last dose nut is coupled to the dosing element by the last dose sleeve. Thus, the device features a last dose protection nut which is progressed as the user dials a dose. This movement may be used to determine the position, where the device is blocked to prevent setting of a higher dose.

The dose limiter is preferably adapted to limit dose selection such that a user cannot set a dose greater than the usable amount in the cartridge. In an ideally cylindrical cartridge, the usable amount may be the full amount left in the cartridge. However, if the cartridge has a necked-down end, it is impossible to fully expel the liquid with a bung running in the cylindrical portion of the cartridge. Thus, a small rest of liquid may remain in the cartridge even after dispensing the dose set prior to the activation of the dose limiter.

A preferred embodiment of the invention comprises a drug delivery device with a (further) nut coupled to the dosing element such that rotation of the dosing element causes an axial movement of the nut in a direction opposite to the direction of the axial movement of the last dose nut. In other words, upon rotation of the dosing element the nut and the last dose nut are both moved axially, however in opposite directions. Preferably, the nut approaches the last dose nut as they are moved axially. Abutment or contact of the nut with the last dose nut may be used to activate the limiter mechanism if a dose is selected corresponding to the amount of liquid left in the cartridge.

The last dose nut may be a full nut or a half nut. Preferably, the last dose nut is a ring or sleeve-like component. The transmission of the rotation of the dosing element into an axial movement of the last dose nut may be achieved by a thread. For the function of the dose limiter of some aspects of the present invention, the last dose nut may either perform a mere axial movement or a combined axial and rotational movement, e.g. on a helical path.

Preferably, the last dose nut engages the stop element on the dosing element when the nut contacts the last dose nut. When there are less than e.g. 120 IU of insulin formulation remaining in the cartridge the last dose protection nut may become engaged with the restriction nut forming a rotary or an axial hard stop with the dosing element.

A further development of this idea involves that the last dose nut comprises an elastically deformable finger with a protrusion, wherein contact of the nut with the last dose nut urges the protrusion into engagement with the at least one stop element. For example, the nut may have a portion overlapping the finger of the last dose nut which urges the finger e.g. radially inwards such that the protrusion engages the stop element. As an alternative, the finger may be flexed outwards to engage the stop element.

According to an embodiment of the invention the dosing element comprises a series of stop elements arranged one behind the other on a helical path. Thus, there are different positions where the dose limiter may be activated. This is helpful if the dose limiter may only be activated during e.g. the last 120 units of the cartridge.

The at least one stop element may have a saw-tooth form. As an alternative, a protrusion or a recess may be provided allowing the last dose nut to engage the stop element such that further relative rotation is prevented.

The dosing element may be any suitable component part of the drug delivery device which performs a rotational movement both during dose setting, i.e. increasing or decreasing the selected dose, and during dose dispensing. This results in the dose indication belt being spooled not only during dose setting but also during dose dispensing such that, after dispensing the whole or a portion of a set dose, the display indicates the remainder of the set dose, which will be zero if the whole dose has been dispensed. Although it is preferred if the dosing element performs a pure rotational movement during dose setting and dose dispensing, i.e. not a combined axial and rotational movement, it is also possible to drive the belt with a dosing element which travels on a helical path during dose setting and/or dose dispensing. The term dosing element is not intended to limit said element to a component which has the sole or main function to select a dose. Moreover, any component part rotating during dose setting and dose dispensing may be the dosing element, even if its main function is e.g. to drive the piston rod, to strain a spring, to transfer a movement from one component part to another, or the like. The dosing element may be a single component part or may comprise two or more components which are e.g. rotationally constrained.

Preferably, the dosing element rotates in a first direction during dose selecting and rotates in a second, opposite direction during dose dispensing. Thus, de-coupling the dosing element and the last dose sleeve during dose dispensing prevents the dose limiter being actuated during dose dispensing. In other words, only an increase in dose selection is blocked by the dose limiter, whereas it is possible to fully dispense any dose selected even when the dose limiter prevents setting of a higher dose.

According to an embodiment of the invention the dosing element comprises a drive sleeve, which has a flange with clutch teeth for coupling the drive sleeve to corresponding teeth of the last dose sleeve, and a transfer sleeve, which is rotationally constrained to the drive sleeve and comprises the stop element. A limited axial movement of the drive sleeve relative to the transfer sleeve may be allowed, e.g. for coupling and de-coupling the clutch teeth.

An example of transferring the rotational movement of the dosing element into an axial movement component involves a threaded engagement. Preferably, the nut comprises a thread engaging a thread on the transfer sleeve. In addition, the last dose nut may comprise a thread engaging a thread of the last dose sleeve.

To allow axial movement of the nut and/or the last dose nut but to prevent relative rotation with respect to a component like the housing of the device, a splined engagement may be provided. Preferably, a housing or chassis is rotationally constrained to the last dose nut and/or the nut. The chassis or housing may include a rib, a bar or a finger to guide the last dose nut and/or the nut.

Preferably, the nut has an additional function in the device. For example, the nut may comprise rotational hard stops and the dosing element may comprise corresponding rotational stops interacting with the rotational hard stops of the nut for limiting axial movement of the nut. Thus, the nut acts as a restriction nut limiting the minimum settable dose (zero IU of insulin formulation) and the maximum settable dose (e.g. 120 IU of insulin formulation).

The dose limiter according to some aspects of the present invention may be used in various types of drug delivery devices including disposable and reusable devices and devices with or without a driving spring. According to a preferred embodiment the drug delivery device comprises a housing, a cartridge holder for retaining the cartridge, a piston rod displaceable relative to the cartridge holder, a driver coupled to the piston rod and at least one clutch, wherein the clutch decouples the driver and the dosing element during dose selecting and couples the driver and the dosing element during dose dispensing. The drug delivery device may further comprise a spring driving the dosing element during dose dispensing.

Preferably, the cartridge contains a medicament. The term “medicament”, as used herein, means a pharmaceutical formulation containing at least one pharmaceutically active compound,

wherein in one embodiment the pharmaceutically active compound has a molecular weight up to 1500 Da and/or is a peptide, a proteine, a polysaccharide, a vaccine, a DNA, a RNA, an enzyme, an antibody or a fragment thereof, a hormone or an oligonucleotide, or a mixture of the above-mentioned pharmaceutically active compound, wherein in a further embodiment the pharmaceutically active compound is useful for the treatment and/or prophylaxis of diabetes mellitus or complications associated with diabetes mellitus such as diabetic retinopathy, thromboembolism disorders such as deep vein or pulmonary thromboembolism, acute coronary syndrome (ACS), angina, myocardial infarction, cancer, macular degeneration, inflammation, hay fever, atherosclerosis and/or rheumatoid arthritis, wherein in a further embodiment the pharmaceutically active compound comprises at least one peptide for the treatment and/or prophylaxis of diabetes mellitus or complications associated with diabetes mellitus such as diabetic retinopathy, wherein in a further embodiment the pharmaceutically active compound comprises at least one human insulin or a human insulin analogue or derivative, glucagon-like peptide (GLP-1) or an analogue or derivative thereof, or exendin-3 or exendin-4 or an analogue or derivative of exendin-3 or exendin-4.

Insulin analogues are for example Gly(A21), Arg(B31), Arg(B32) human insulin; Lys(B3), Glu(B29) human insulin; Lys(B28), Pro(B29) human insulin; Asp(B28) human insulin; human insulin, wherein proline in position B28 is replaced by Asp, Lys, Leu, Val or Ala and wherein in position B29 Lys may be replaced by Pro; Ala(B26) human insulin; Des(B28-B30) human insulin; Des(B27) human insulin and Des(B30) human insulin.

Insulin derivates are for example B29-N-myristoyl-des(B30) human insulin; B29-N-palmitoyl-des(B30) human insulin; B29-N-myristoyl human insulin; B29-N-palmitoyl human insulin; B28-N-myristoyl LysB28ProB29 human insulin; B28-N-palmitoyl-LysB28ProB29 human insulin; B30-N-myristoyl-ThrB29LysB30 human insulin; B30-N-palmitoyl-ThrB29LysB30 human insulin; B29-N—(N-palmitoyl-Y-glutamyl)-des(B30) human insulin; B29-N—(N-lithocholyl-Y-glutamyl)-des(B30) human insulin; B29-N-(ω-carboxyheptadecanoyl)-des(B30) human insulin and B29-N-(ω-carboxyheptadecanoyl) human insulin.

Exendin-4 for example means Exendin-4(1-39), a peptide of the sequence H-His-Gly-Glu-Gly-Thr-Phe-Thr-Ser-Asp-Leu-Ser-Lys-Gln-Met-Glu-Glu-Glu-Ala-Val-Arg-Leu-Phe-Ile-Glu- Trp-Leu-Lys-Asn-Gly-Gly-Pro-Ser-Ser-Gly-Ala-Pro-Pro-Pro-Ser-NH2.

Exendin-4 derivatives are for example selected from the following list of compounds:

H-(Lys)4-des Pro36, des Pro37 Exendin-4(1-39)-NH2,

H-(Lys)5-des Pro36, des Pro37 Exendin-4(1-39)-NH2,

des Pro36 Exendin-4(1-39),

des Pro36 [Asp28] Exendin-4(1-39),

des Pro36 [IsoAsp28] Exendin-4(1-39),

des Pro36 [Met(O)14, Asp28] Exendin-4(1-39),

des Pro36 [Met(O)14, IsoAsp28] Exendin-4(1-39),

des Pro36 [Trp(O2)25, Asp28] Exendin-4(1-39),

des Pro36 [Trp(O2)25, IsoAsp28] Exendin-4(1-39),

des Pro36 [Met(O)14 Trp(O2)25, Asp28] Exendin-4(1-39),

des Pro36 [Met(O)14 Trp(O2)25, IsoAsp28] Exendin-4(1-39); or

des Pro36 [Asp28] Exendin-4(1-39),

des Pro36 [IsoAsp28] Exendin-4(1-39),

des Pro36 [Met(O)14, Asp28] Exendin-4(1-39),

des Pro36 [Met(O)14, IsoAsp28] Exendin-4(1-39),

des Pro36 [Trp(O2)25, Asp28] Exendin-4(1-39),

des Pro36 [Trp(O2)25, IsoAsp28] Exendin-4(1-39),

des Pro36 [Met(O)14 Trp(O2)25, Asp28] Exendin-4(1-39),

des Pro36 [Met(O)14 Trp(O2)25, IsoAsp28] Exendin-4(1-39),

wherein the group -Lys6-NH2 may be bound to the C-terminus of the Exendin-4 derivative;

or an Exendin-4 derivative of the sequence

des Pro36 Exendin-4(1-39)-Lys6-NH2 (AVE0010),

H-(Lys)6-des Pro36 [Asp28] Exendin-4(1-39)-Lys6-NH2,

des Asp28 Pro36, Pro37, Pro38Exendin-4(1-39)-NH2,

H-(Lys)6-des Pro36, Pro38 [Asp28] Exendin-4(1-39)-NH2,

H-Asn-(Glu)5des Pro36, Pro37, Pro38 [Asp28] Exendin-4(1-39)-NH2,

des Pro36, Pro37, Pro38 [Asp28] Exendin-4(1-39)-(Lys)6-NH2,

H-(Lys)6-des Pro36, Pro37, Pro38 [Asp28] Exendin-4(1-39)-(Lys)6-NH2,

H-Asn-(Glu)5-des Pro36, Pro37, Pro38 [Asp28] Exendin-4(1-39)-(Lys)6-NH2,

H-(Lys)6-des Pro36 [Trp(O2)25, Asp28] Exendin-4(1-39)-Lys6-NH2,

H-des Asp28 Pro36, Pro37, Pro38 [Trp(02)25] Exendin-4(1-39)-NH2,

H-(Lys)6-des Pro36, Pro37, Pro38 [Trp(O2)25, Asp28] Exendin-4(1-39)-NH2,

H-Asn-(Glu)5-des Pro36, Pro37, Pro38 [Trp(O2)25, Asp28] Exendin-4(1-39)-NH2,

des Pro36, Pro37, Pro38 [Trp(O2)25, Asp28] Exendin-4(1-39)-(Lys)6-NH2,

H-(Lys)6-des Pro36, Pro37, Pro38 [Trp(O2)25, Asp28] Exendin-4(1-39)-(Lys)6-NH2,

H-Asn-(Glu)5-des Pro36, Pro37, Pro38 [Trp(O2)25, Asp28] Exendin-4(1-39)-(Lys)6-NH2,

H-(Lys)6-des Pro36 [Met(O)14, Asp28] Exendin-4(1-39)-Lys6-NH2,

des Met(O)14 Asp28 Pro36, Pro37, Pro38 Exendin-4(1-39)-NH2,

H-(Lys)6-desPro36, Pro37, Pro38 [Met(O)14, Asp28] Exendin-4(1-39)-NH2,

H-Asn-(Glu)5-des Pro36, Pro37, Pro38 [Met(O)14, Asp28] Exendin-4(1-39)-NH2,

des Pro36, Pro37, Pro38 [Met(O)14, Asp28] Exendin-4(1-39)-(Lys)6-NH2,

H-(Lys)6-des Pro36, Pro37, Pro38 [Met(O)14, Asp28] Exendin-4(1-39)-(Lys)6-NH2,

H-Asn-(Glu)5 des Pro36, Pro37, Pro38 [Met(O)14, Asp28] Exendin-4(1-39)-(Lys)6-NH2,

H-Lys6-des Pro36 [Met(O)14, Trp(O2)25, Asp28] Exendin-4(1-39)-Lys6-NH2,

H-des Asp28 Pro36, Pro37, Pro38 [Met(O)14, Trp(02)25] Exendin-4(1-39)-NH2,

H-(Lys)6-des Pro36, Pro37, Pro38 [Met(O)14, Asp28] Exendin-4(1-39)-NH2,

H-Asn-(Glu)5-des Pro36, Pro37, Pro38 [Met(O)14, Trp(O2)25, Asp28] Exendin-4(1-39)-NH2,

des Pro36, Pro37, Pro38 [Met(O)14, Trp(O2)25, Asp28] Exendin-4(1-39)-(Lys)6-NH2,

H-(Lys)6-des Pro36, Pro37, Pro38 [Met(O)14, Trp(O2)25, Asp28] Exendin-4(S1-39)-(Lys)6-NH2,

H-Asn-(Glu)5-des Pro36, Pro37, Pro38 [Met(O)14, Trp(O2)25, Asp28] Exendin-4(1-39)-(Lys)6-NH2,

or a pharmaceutically acceptable salt or solvate of any one of the afore-mentioned Exendin-4 derivative.

Hormones are for example hypophysis hormones or hypothalamus hormones or regulatory active peptides and their antagonists as listed in Rote Liste, ed. 2008, Chapter 50, such as Gonadotropine (Follitropin, Lutropin, Choriongonadotropin, Menotropin), Somatropine (Somatropin), Desmopressin, Terlipressin, Gonadorelin, Triptorelin, Leuprorelin, Buserelin, Nafarelin, Goserelin.

A polysaccharide is for example a glucosaminoglycane, a hyaluronic acid, a heparin, a low molecular weight heparin or an ultra low molecular weight heparin or a derivative thereof, or a sulphated, e.g. a poly-sulphated form of the above-mentioned polysaccharides, and/or a pharmaceutically acceptable salt thereof. An example of a pharmaceutically acceptable salt of a poly-sulphated low molecular weight heparin is enoxaparin sodium.

Antibodies are globular plasma proteins (˜150 kDa) that are also known as immunoglobulins which share a basic structure. As they have sugar chains added to amino acid residues, they are glycoproteins. The basic functional unit of each antibody is an immunoglobulin (Ig) monomer (containing only one Ig unit); secreted antibodies can also be dimeric with two Ig units as with IgA, tetrameric with four Ig units like teleost fish IgM, or pentameric with five Ig units, like mammalian IgM.

The Ig monomer is a “Y”-shaped molecule that consists of four polypeptide chains; two identical heavy chains and two identical light chains connected by disulfide bonds between cysteine residues. Each heavy chain is about 440 amino acids long; each light chain is about 220 amino acids long. Heavy and light chains each contain intrachain disulfide bonds which stabilize their folding. Each chain is composed of structural domains called Ig domains. These domains contain about 70-110 amino acids and are classified into different categories (for example, variable or V, and constant or C) according to their size and function. They have a characteristic immunoglobulin fold in which two β sheets create a “sandwich” shape, held together by interactions between conserved cysteines and other charged amino acids.

There are five types of mammalian Ig heavy chain denoted by α, δ, ε, γ, and μ. The type of heavy chain present defines the isotype of antibody; these chains are found in IgA, IgD, IgE, IgG, and IgM antibodies, respectively.

Distinct heavy chains differ in size and composition; α and γ contain approximately 450 amino acids and δ approximately 500 amino acids, while μ and ε have approximately 550 amino acids. Each heavy chain has two regions, the constant region (CH) and the variable region (VH). In one species, the constant region is essentially identical in all antibodies of the same isotype, but differs in antibodies of different isotypes. Heavy chains γ, α and δ have a constant region composed of three tandem Ig domains, and a hinge region for added flexibility; heavy chains μ and ε have a constant region composed of four immunoglobulin domains. The variable region of the heavy chain differs in antibodies produced by different B cells, but is the same for all antibodies produced by a single B cell or B cell clone. The variable region of each heavy chain is approximately 110 amino acids long and is composed of a single Ig domain.

In mammals, there are two types of immunoglobulin light chain denoted by λ and κ. A light chain has two successive domains: one constant domain (CL) and one variable domain (VL). The approximate length of a light chain is 211 to 217 amino acids. Each antibody contains two light chains that are always identical; only one type of light chain, κ or λ, is present per antibody in mammals.

Although the general structure of all antibodies is very similar, the unique property of a given antibody is determined by the variable (V) regions, as detailed above. More specifically, variable loops, three each the light (VL) and three on the heavy (VH) chain, are responsible for binding to the antigen, i.e. for its antigen specificity. These loops are referred to as the Complementarity Determining Regions (CDRs). Because CDRs from both VH and VL domains contribute to the antigen-binding site, it is the combination of the heavy and the light chains, and not either alone, that determines the final antigen specificity.

An “antibody fragment” contains at least one antigen binding fragment as defined above, and exhibits essentially the same function and specificity as the complete antibody of which the fragment is derived from. Limited proteolytic digestion with papain cleaves the Ig prototype into three fragments. Two identical amino terminal fragments, each containing one entire L chain and about half an H chain, are the antigen binding fragments (Fab). The third fragment, similar in size but containing the carboxyl terminal half of both heavy chains with their interchain disulfide bond, is the crystalizable fragment (Fc). The Fc contains carbohydrates, complement-binding, and FcR-binding sites. Limited pepsin digestion yields a single F(ab′)2 fragment containing both Fab pieces and the hinge region, including the H—H interchain disulfide bond. F(ab′)2 is divalent for antigen binding. The disulfide bond of F(ab′)2 may be cleaved in order to obtain Fab′. Moreover, the variable regions of the heavy and light chains can be fused together to form a single chain variable fragment (scFv).

Pharmaceutically acceptable salts are for example acid addition salts and basic salts. Acid addition salts are e.g. HCl or HBr salts. Basic salts are e.g. salts having a cation selected from alkali or alkaline, e.g. Na+, or K+, or Ca2+, or an ammonium ion N+(R1)(R2)(R3)(R4), wherein R1 to R4 independently of each other mean: hydrogen, an optionally substituted C1-C6-alkyl group, an optionally substituted C2-C6-alkenyl group, an optionally substituted C6-C10-aryl group, or an optionally substituted C6-C10-heteroaryl group. Further examples of pharmaceutically acceptable salts are described in “Remington's Pharmaceutical Sciences” 17. ed. Alfonso R. Gennaro (Ed.), Mark Publishing Company, Easton, Pa., U.S.A., 1985 and in Encyclopedia of Pharmaceutical Technology.

Pharmaceutically acceptable solvates are for example hydrates.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 shows a sectional view of a drug delivery device;

FIG. 2 shows a cut-away view of a drug delivery device of FIG. 1;

FIG. 3 shows an enlarged detail of FIG. 1;

FIG. 4 shows a sectional view of a detail of the drug delivery device of FIG. 1;

FIGS. 5a, b show cut-away views of a further detail of the drug delivery device of FIG. 1;

FIG. 6 shows a cut-away view of a further detail of the drug delivery device of FIG. 1;

FIG. 7a shows a cut-away view of a detail of the drug delivery device of FIG. 1;

FIG. 7b shows a sectional view of the detail of FIG. 7 a;

FIG. 8 shows a cut-away view of the display of the drug delivery device of FIG. 1;

FIG. 9 shows a sectional view of the display of FIG. 8;

FIG. 10 shows a sectional view of the display of FIG. 8;

FIG. 11 shows a cut-away view of a further detail of the drug delivery device of FIG. 1;

FIG. 12 shows a sectional view of the detail of FIG. 11;

FIGS. 13a, b show perspective views of the proximal end of the drug delivery device of FIG. 1 in different positions;

FIG. 14 shows a cut-away view of a detail of the drug delivery device of FIG. 1;

FIG. 15 shows a perspective view of a detail of the drug delivery device of FIG. 1;

FIGS. 16a-c show cut-away views of details of the drug delivery device of FIG. 1 during dose setting; and

FIGS. 17a-c show cut-away views of details of the drug delivery device of FIG. 1 during dose dispensing.

DETAILED DESCRIPTION

FIG. 1 shows a drug delivery device 1 in the form of an injection pen. The device has a distal end (upper end in FIG. 1) and a proximal end (lower end in FIG. 1). The component parts of the drug delivery device 1 are shown in FIGS. 2 and 3 in more detail. The drug delivery device 1 comprises an outer housing 10, an inner body or chassis 20, a piston rod 30, a driver 40, a nut 50, a display 60, a button 70, a cartridge 80, a torsion spring 90, a drive nut 100, a last dose nut 110, a last dose sleeve 120, a transfer sleeve 130, a dose selector 140 and a return spring 150. A needle arrangement (not shown) with a needle hub and a needle cover may be provided as additional components, which can be exchanged as explained above.

The outer housing 10 is a generally tubular element having a distal part, which forms a cartridge holder 11 for receiving cartridge 80, and a proximal part for receiving the dosing mechanism. In a preferred embodiment, the outer housing 10 has a circular cross-section in the region of the cartridge holder 11 and in the intermediate region where the cartridge holder merges with the outer housing part covering the dosing mechanism, whereas the proximal region of the housing 10 has a triangular cross-section. Thus, it is comfortable to hold and handle the device 1. A window 12 is provided in the outer housing 10 allowing to view a detail of the display 60. The cartridge holder 11 may be a single-component part with the outer housing 10 or a separate component part attached to the outer housing 10 during assembly. As explained below in more detail, a portion of the outer housing 10 is provided with radially inwardly orientated teeth 13 forming a clutch with driver 40.

The chassis 20 is a generally tubular element which is axially and rotationally fixed within the outer housing 10. A flange may be provided attach a fee end of spring 90. Further, at least one splined finger 21 is provided which extends in the distal direction. In the embodiment shown in the Figures, three fingers 21 are provided each guiding the nut 50 and the last dose nut 110.

The piston rod 30 is an elongate element having an external thread 31 which is engages the drive nut 100. Further, the piston rod comprises a spline 32 or the like alignment means for rotationally coupling the piston rod 30 in the outer housing 10 but allowing axial displacement of the piston rod 30 relative to the outer housing 10. A bearing 33 is provided at the distal end of piston rod 30.

The driver 40 has a generally tubular distal portion which at least partly surrounds the piston rod 30. A proximal portion of the driver may have a smaller diameter. This proximal portion is a solid bar in the embodiment depicted in the figures but may as well be tubular. A flange 41 is provided at the distal end of the driver 40. As will be explained below in more detail, the flange comprises distally orientated teeth 42 forming a clutch which couples or decouples the driver to the drive nut 100. Further teeth 43 are provided on the proximal face of the flange 41 which are part of a clutch which couples or decouples the driver to the last dose sleeve 120. The driver 40 is splined to the transfer sleeve 130 to prevent relative rotation.

In addition, a clutch is provided between the radially outer surface of flange 41 and outer housing 10. As shown in FIG. 4, this clutch may be formed as a ratchet with a ratchet finger 44 on the driver 40 and teeth 13 on an inner surface of the outer housing 10. The clutch allows stepwise rotation in a first direction during dose setting (dose increasing) but is designed to withstand the torque of torsion spring 90. The clutch is designed such that a user can overcome the clutch, i.e. reduce a set dose such that finger 44 overrides teeth 13 in a rotation opposite the first direction.

The nut 50 is provided between the transfer sleeve 130 and the chassis 20. External ribs of the nut 50 engage inner splines of the chassis 20. An internal thread of the nut 50 engages an external thread of the transfer sleeve 130. As an alternative, splines and ribs could be provided on the interface between the nut 50 and the transfer sleeve 130 and threads could be provided on the interface between the nut 50 and the chassis 20. As a further alternative, the nut 50 may be designed as e.g. a half nut. Further, in the embodiment of FIGS. 5a, 5b and 11, rotational hard stops 51, 52 are provided on nut 50 for interaction with corresponding stops on the transfer sleeve 130. As depicted in FIGS. 5a and 7a , there are three slots or grooves 53 on the outer surface of the nut 50. Fingers 21 of the chassis 20 engage these grooves 53 rotationally constraining the nut 50 with respect to chassis 20 but allowing relative axial movement.

The display 60 comprises in the embodiment shown in FIGS. 8 to 10 a first belt 61 and a second belt 62 each having a series of numbers or the like symbols thereon and each having a series of apertures 63 and 64, respectively, which are arranged in uniform distribution with equal distance between the apertures. However, the size and/or the distances between apertures 63 and between apertures 64 may be different. The first belt 61 is driven via a drive gear 134 provided on the transfer sleeve 130, a transfer gear set 65, having two rotationally coupled gear wheels, and a transfer gear and sprocket set 66. A first gear wheel of the transfer gear set 65 meshes with the drive gear 134 and the second gear wheel of the transfer gear set 65 meshes with a transfer gear wheel of the transfer gear and sprocket set 66, which further comprises a sprocket rotationally coupled to the transfer gear wheel and engaging with protrusions 67 the apertures 63 of the first belt. Thus, rotation of the transfer sleeve 130 spools the first belt 61. The second belt 62 is driven by a sprocket 135 of the transfer sleeve 130 which has in the embodiment shown in the Figures two protrusions 136 engaging the apertures 64 in the second belt 62. Thus, the second belt 62 is directly coupled to the transfer sleeve 130. As the distance between protrusions 136 is much bigger than the distance between apertures 64, a continuous rotation of the transfer sleeve 130 is translated into an intermittent motion of the second belt 62.

Both belts 61, 62 are guided on a striker plate 68 which is fixed within the outer housing 10. The striker plate 68 has a flat or arched surface such that the part of the belts guided on the striker plate 68 has a curvature which is lower than the curvature of the cylindrical portion of the outer housing 10. Due to the striker plate 68, the outer housing 10 has its (rounded) triangular shape as indicated in FIGS. 9 and 10. In the embodiment depicted in the Figures, the first belt 61 is guided by the striker plate 68 and the sprocket of the transfer gear and sprocket set 66 on a generally triangular closed loop. The second belt may further be guided by suitable means to form a folded closed loop as indicated in FIGS. 8 and 10.

The button 70 forms the proximal end of the device and is held within dose selector 140 to allow relative rotation to the dose selector 140 and limited axial movement. A centrally locates stem 71 abuts with its distal end face the proximal end face of the proximal part of driver 40. Thus, axial movement of button 70 is directly transferred to driver 40.

The cartridge 80 includes a pre-filled, necked-down cartridge reservoir 81, which may be typically made of glass. A rubber type bung 82 or stopper is located at the proximal end of the cartridge reservoir 81, and a pierceable rubber seal (not shown) is located at the other, distal, end. A crimped annular metal band 83 is used to hold the rubber seal in place. The cartridge 80 is provided within the cartridge holder 11 with bearing 33 of piston rod 30 abutting bung 82.

The drug delivery device 1 is intended to accept a 1.5 mL cartridge or a 3.0 mL cartridge, but the design could be adapted to accept other medicament container sizes or formats. The embodiment of the device depicted in the Figures is designed to be disposable in that the cartridge 80 cannot be replaced by the user or healthcare professional. A reusable variant of the device would involve making the cartridge holder removable and allowing the resetting of the piston rod 30.

The torsion spring 90 has two free ends, wherein the distal end is attached to the flange 41 of the driver 40 and the proximal end is attached to a flange of the stationary chassis 20. Thus, rotation of the driver 40 relative to the chassis 20 strains the torsion spring 90 and the stored energy may be released by allowing the driver 40 to rotate relative to the chassis 20. The torsion spring 20 may be assembled in a pre-strained state to provide sufficient torque even for dispensing small doses. In an alternative embodiment the spring may be pre-charged such that the stored energy is sufficient to dispense the whole contents of a full cartridge.

The drive nut 100 is a sleeve-like or disk-shaped component which has an inner thread engaging the thread 31 of the piston rod 30. The drive nut 100 is held within the outer housing 10 such that the drive nut 100 is allowed to freely rotate. In the embodiment shown in the Figures, the drive nut 100 comprises a flange 101 which forms a contact surface for the return spring 150 which is interposed between the driver 40 and the drive nut 100. Further, teeth 102 are provided for engagement with teeth 42 of driver 40.

The last dose nut 110 is provided interposed between the driver 40 and the chassis finger 21. A splined engagement between the chassis finger 21 and the drive nut 110 allows axial movement of the last dose nut 110 but prevents relative rotation with respect to the chassis 20. The last dose nut is provided with an outer thread 111. Further, an elastically deformable finger 112 is provided on the last dose nut 110. FIG. 7a shows in more detail that the last dose nut 110 has the outer thread 111 interrupted by one or more (in the present embodiment three) groove-like axially extending recesses 113, each of which may be guided on a respective finger 21 of the chassis 20. A further recessed portion 114 is designed and arranged to receive a rib-like axially extending protrusion 54 of nut 50.

The last dose sleeve 120 cooperates with the last dose nut 110 and nut 50 to form a last dose mechanism preventing setting of a dose which increases the amount of liquid left in the cartridge 80. The last dose sleeve 120 is a hollow component having an internal thread 121 which engages outer thread 111 of the last dose nut 110. A distal end face of the last dose sleeve 120 is provided with teeth 122 interacting with the teeth 43 provided on the proximal face of the flange 41 for rotationally coupling the last dose sleeve 120 to the driver 40.

The transfer sleeve 130 is a tubular element which is splined to the driver 40 such that it is rotationally constrained to the driver 40 but allows relative axial movement with respect to the driver. As mentioned above, the transfer sleeve 130 has a distal portion provided with thread 131 and rotational stops 132, 133. Further, the transfer sleeve 130 is provided with gear 134 for driving the first belt 61 and a sprocket 135 with protrusions 136 for driving the second belt 62. A stepped portion of the transfer sleeve 130 corresponds to the change in diameter of the driver 40 such that axial movement of the driver 40 relative to the transfer sleeve 130 is limited in the proximal direction. FIGS. 5a and 5b show saw-toothed stop elements 137 provided on the transfer sleeve 130 for interaction with the last dose nut 110.

The dose selector 140 has a triangular outer shape which corresponds to the outer shape of the proximal part of the outer housing 10. The dose selector 140 comprises an inner sleeve 141 guiding the stem 71 of the button 70 and receiving the proximal end of driver 40. As depicted in FIGS. 14 and 15 the proximal end of driver 40 has splines 45 engaging an inner guiding contour of the dose selector.

The return spring 150 is a compression spring which is located between flange 101 of drive nut 100 and flange 41 of driver 40. Thus, return spring 150 urges the driver 40 in the proximal direction. If button 70 is pushed by a user, driver 40 is moved in the distal direction against the bias of return spring 150.

In the following, the function of the disposable drug delivery device 1 and its components will be explained in more detail.

To use the device, a user has to select a dose. In the start (at rest) condition as shown in FIGS. 1 to 3 and 16 a to 16 c the torsion spring 90 has enough preload such that if the user selects the minimum dose the device will be able to deliver that minimum dose. At rest the dose indicator belts 61, 62 display 0 or the equivalent marking to show that no dose has been selected.

A priming and/or safety shots may be required prior to an injection. Priming is the act of preparing the device for first use. In existing pen injectors this means setting and delivering one or more small doses into air so that the ‘play’ (any clearances) and tolerances in the device are removed and that components are placed into suitable compression or tension. Safety shots are where the user sets and delivers one or more small doses into air before each injection to ensure that the needle is not blocked.

The user sets a dose by rotating the dose selector 140. Rotating the dose selector 140 rotates the driver 40 and adds preload to the torsion spring 90. The transfer sleeve 130 is splined to the driver 40 and indexes the dose number mechanism of display 60 when the user dials the dose selector 140.

FIG. 4 shows the ratchet features 41 on the driver 40 that engage with splines 13 on the internal surface of the outer housing 10 to prevent the dose selector 140 rotating back to its initial position due to the torsion spring torque. These ratchet features 13, 41 become disengaged when the user fully depresses the injection button 70.

As the user sets a dose by rotating the dose selector 140 and hence the driver 40 and the transfer sleeve 130 nut 50 travels axially guided by fingers 21 and grooves 53. Simultaneously, last dose nut 110 travels axially guided by fingers 21 and recesses 113. The threaded engagement of the nut 50 with transfer sleeve 130 and the threaded engagement of last dose nut 110 with last dose sleeve 120 is such that, the nut 50 approaches the last dose nut 110 if the user increases the dose and that they depart from each other if the user reduces the dose. In its unstressed position, the finger 112 is positioned such that it does not interfere with the stop elements 137 provided on the transfer sleeve 130.

Limits for a minimum dose (0 IU) and a maximum dose (e.g. 120 IU) are provided by hard stop features on the nut 50 which interfere with features 132, 133 on the transfer sleeve 130 and therefore prevent further relative rotation. FIGS. 5a and 5b show the nut 50 in an intermediate position, i.e. with about 60 IU dialed.

A last dose protection prevents the user from setting a dose greater than the available volume in the cartridge 80. During dose setting, the driver 40 is engaged with the last dose sleeve 120 via teeth 43 and 122. When the cartridge volume falls below 120 units the last dose nut 110 has moved in to a position where it can interfere with the nut 50. When the user attempts to dial a dose greater than that remaining, the nut 50 bends a flexible feature, i.e. finger 112, on the last dose nut 110 such that it engages with step-like spline features 137 on the transfer sleeve 130 to form a rotary hard stop. FIGS. 7a and 7b show the device shortly before engagement of this last dose mechanism. This step of bending the finger 112 inwardly to engage one of the stop elements 137 is initiated by the nut 50 approaching the last dose nut 110 such that protrusion 54 enters recess 114 such that the inner surface of protrusion 54 presses on finger 112. As soon as finger 112 engages one of stop elements 137, further rotation of the last dose nut 110 in the direction increasing the set dose is prevented. Because the last dose nut 110 is in threaded engagement with the last dose sleeve 120 which in turn in coupled to the drive sleeve 40 and thus via transfer sleeve 130 to the dose selector 140, the whole dose setting mechanism is blocked thus limiting the dose which a user can select. However, an opposite movement, i.e. reducing a dose is still possible. In addition, the set dose can be fully administered even with the finger 112 engaging a stop element 137.

The dose number is increased or reduced as the dose selector 140 is rotated. This is achieved via a spur gear feature 134 within the transfer sleeve 130 engaging with a gearbox 65 to a sprocket 66 which indexes the corresponding number belt 61. The second number belt 62 may be indexed by coupling a secondary feature (protrusion 136) on the transfer sleeve 130 to an additional gearbox or directly to the second belt 62. In the embodiment shown in FIGS. 8 to 10, the first number belt 61 may be provided with numbers “0” to “9” twice, and the second number belt 62 may have the numbers “0” to “12” thereon. Instead of the “0” on the second belt 62, a blank may be provided. In other words, for every full rotation of dose selector 140 the first belt 61 (the single units counter belt) makes a full revolution displaying the numbers “0” to “9” twice. At the same time, the second belt 62 (ten units counter belt) intermittently moves by two position, i.e. for example from blank to “1” and from “1” to “2”. Starting from zero units dialed, a full revolution of dose selector 140 will result in a display showing “2” on the second belt 62 and “0” on the first belt 61, such that belts 61 and 62 together display “20”.

When the injection button 70 is pressed the following actions take place which can be understood comparing FIGS. 16a to 16c (button 70 released) with FIGS. 17a to 17c (button 70 pressed):

The driver 40 is moved forward by the injection button 70 and disengages from the last dose sleeve 120. The last dose protection nut 110 thus remains static throughout an injection. Further, the driver 40 begins to compress the return spring 150 and engages with the lead screw drive nut 100 via clutch teeth 42, 102. At this point the driver 40 is still engaged with the energy storage ratchet 13, 41 to prevent the torsion spring 90 from unwinding. The driver 40 disengages from the dose selector 140 which may now be rotated freely without influencing injection or dial dose. Over the last 1 mm or so the driver 40 becomes fully engaged with the drive nut 100 and moves off the energy storage ratchet 13, 41. The torsion spring 90 begins to unwind rotating the driver 40 which in turn spins the drive nut 100. As the drive nut 100 rotates the piston rod 30 (lead screw), which is splined to the device outer housing 10, moves forwards dispensing the medication.

Dose interruption and dose splitting is possible. If the axial force on the injection button 70 is removed, the button 70 returns to its initial axial position relative to the dose selector 140 under the action of return spring 150. This allows the ratchets 41 on the driver 40 to engage with the splines 13 of the outer housing 10, thus preventing further injection due to the driving torque of the torsion spring 90. Further, this reengages the driver 40 with the dose selector 140 and the last dose sleeve 120, thus allowing the dose selector 140 to rotate again. At this point the dose selector 140 will realign with the outer housing 10 as explained below. The dose can be changed by rotating the dose selector 140 and pressing the button 70 restarts the injection manoeuvre.

During injection the torsion spring 90 will unwind, rotating the driver 40. This will index the dose number mechanism such that the number counts down towards “0”. At the same time the nut 50 moves back towards its “0” position. When the nut 50 has reached this position the user will hear and possibly feel a “click” to signify end of dose. This is achieved by features on both the nut 40 and the transfer sleeve 130 passing over each other with slight detent interference as shown in FIGS. 11 and 12.

This exemplary embodiment has a non-axisymmetric outer housing 10 and dose selector 140 which means that the dose selector 140 becomes ‘misaligned’ relative to the outer housing 10 during dose setting. FIGS. 13a and 13b show the dose selector 140 aligned and misaligned, respectively. There is no technical problem with this but users may prefer that the dose selector 140 is realigned to the outer housing 10 at the end of each injection. Therefore the device includes a mechanism for realigning the dose selector 140 with the device outer housing 10 when the user releases the button 70. As depicted in FIGS. 14 and 15, when the user releases the button, the driver 40 moves axially back to its “0” position. As the driver 40 comes in to contact with the dose selector 140, male location features (splines 45) on the driver 40 begin to engage with corresponding female helical features 142 located within the dose selector 140. This causes the dose selector 140 to rotate until it becomes fully engaged with the driver 40. The dose selector 140 is then fully aligned with the outer housing 10.

Like many other pen injectors which use a threaded nut or half nut mechanism to achieve last dose protection the dose limiter of some aspects of the present invention operates across the entire volume of the cartridge, e.g. 3 ml for a 300 IU, U100 insulin cartridge. The last dose protection nut is progressed as the user dials a dose. When there is less than the maximum settable dose, e.g. 120 IU of insulin formulation, remaining in the cartridge the last dose protection nut becomes engaged with the restriction nut forming a rotary or an axial hard stop with the transfer sleeve. 

The invention claimed is:
 1. A drug delivery device comprising: a cartridge containing liquid; a dose limiter configured to inhibit setting of a dose exceeding an amount of the liquid left in the cartridge; a dosing element rotatable during dose selecting; a last dose nut coupled to the dosing element during the dose selecting such that rotation of the dosing element causes an axial movement of the last dose nut; and a stop element configured to block further movement of the last dose nut if the selected dose corresponds to the amount of the liquid left in the cartridge, wherein the stop element is on the dosing element, wherein the dose limiter further comprises a last dose sleeve rotationally coupled to the dosing element during the dose selecting and rotationally decoupled from the dosing element during dose dispensing, and the last dose nut is coupled to the dosing element by the last dose sleeve.
 2. The drug delivery device of claim 1, further comprising a nut coupled to the dosing element such that rotation of the dosing element causes an axial movement of the nut in a direction opposite to the direction of the axial movement of the last dose nut.
 3. The drug delivery device of claim 2, wherein the nut comprises rotational hard stops and wherein the dosing element comprises corresponding rotational stops interacting with the rotational hard stops of the nut for limiting the axial movement of the nut.
 4. The drug delivery device of claim 2, wherein the nut contacts the last dose nut if the selected dose corresponds to the amount of the liquid left in the cartridge.
 5. The drug delivery device of claim 4, wherein the last dose nut engages the stop element when the nut contacts the last dose nut.
 6. The drug delivery device of claim 5, wherein the last dose nut comprises an elastically deformable finger with a protrusion, wherein contact of the nut with the last dose nut urges the protrusion into engagement with the stop element.
 7. The drug delivery device of claim 1, wherein the dosing element comprises a series of stop elements arranged one behind the other on a helical path.
 8. The drug delivery device of claim 1, wherein the stop element has a saw-tooth form.
 9. The drug delivery device of claim 1, wherein the dosing element rotates in a first direction during the dose selecting and rotates in a second, opposite direction during the dose dispensing.
 10. The drug delivery device of claim 1, wherein: the dosing element comprises a drive sleeve, which has a flange with clutch teeth for coupling the drive sleeve to corresponding teeth of the last dose sleeve, and a transfer sleeve, which is rotationally constrained to the drive sleeve and comprises the stop element.
 11. The drug delivery device of claim 10, further comprising a nut comprising a thread engaging a thread on the transfer sleeve.
 12. The drug delivery device of claim 1, wherein the last dose nut comprises a thread engaging a thread of the last dose sleeve.
 13. The drug delivery device of claim 1, further comprising a housing or chassis rotationally constrained to the last dose nut.
 14. The drug delivery device of claim 1, further comprising: a housing; a cartridge holder for retaining the cartridge; a piston rod displaceable relative to the cartridge holder; and a driver coupled to the piston rod and at least one clutch, wherein the clutch decouples the driver and the dosing element during the dose selecting and couples the driver and the dosing element during the dose dispensing.
 15. The drug delivery device of claim 1, further comprising a spring driving the dosing element during the dose dispensing.
 16. The drug delivery device of claim 1, wherein the liquid is a medicament to be dispensed from the drug delivery device.
 17. A method of operating a drug delivery device, the method comprising: rotating a dose selector to select a dose corresponding to an amount of liquid left in a cartridge of the drug delivery device, whereby rotation of the dose selector causes a last dose nut to move axially through the drug delivery device, and rotation of the dose selector to select the dose corresponding to the amount of the liquid causes a stop element to block further axial movement of the last dose nut; and dispensing at least a portion of the selected dose.
 18. The method of claim 17, wherein: dispensing at least the portion of the selected dose comprises pressing a button to cause a dosing element to advance to dispense at least a portion of the selected dose, and rotating the dose selector causes the last dose nut to move axially through the drug delivery device toward a nut coupled to the dosing element and causes the nut to move axially through the drug delivery device through the last dose nut.
 19. The method of claim 18, wherein rotating the dose selector causes the nut to contact the last dose nut such that the last dose nut engages the stop element, thereby blocking further axial movement of the last dose nut.
 20. The method of claim 19, wherein rotating the dose selector causes an elastically deformable finger of the last dose nut to engage the stop element, thereby blocking further axial movement of the last dose nut. 